From the width of the thumbnail and the width of the image, you could only recover with 25% quality using the proposed method. I have never used any jpeg recovery software, but there are companies that say they can do it.
– PhilFeb 17 '13 at 19:29

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You'll probably need to experiment with programs like Photoshop (or even Paint.NET). They can all enlarge the thumbnail but will have different algorithms to do the interpolation. You might find that you need to use different methods for different photos.
– ChrisFFeb 17 '13 at 19:29

@ChrisF Maybe what I'm searching for is a program that uses existing HD image as template and then enlarges thumbnail using same patterns. And I would love to start learning about JPG recovery and start writing program for it, but unfortunately I have no time to do that.
– skmasqFeb 17 '13 at 19:32

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@skmasq: You might want to see if here are actual recovery tools that can fix, or at least bypass, the problem in the JPEGs. Such issues are usually caused by only a few blocks of the image being bad, and the rest of the image likely still exists. If you could find a tool that will open the photo and load as much of it as possible, you might be able to fix any bad spots with the content-aware tools of Photoshop Elements or CS5/6.
– jrista♦Feb 17 '13 at 20:12

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@jrista Ok I will try that, but the thing is, this is allready recovered image, before I couldn't even open it.
– skmasqFeb 17 '13 at 20:46

1 Answer
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In the case of this picture it might be an improvement because the missing part was not the most interesting part (not the eye-catcher) of the picture and it being blurry after reconstruction from the thumbnail does not completely ruin the picture.

In other cases, though, this method will make faces look like ugly blobs next to sharp ones. All hope to gain anything by this method is probably lost then.

I know of no tool which does this. The reparation I did manually using GIMP. I loaded both JPG files, resized the thumbnail image to the dimensions of the original file, copied this as a new (lower) layer in the original file and made the gray part of the corrupted file transparent.